The invention relates to a method and apparatus regarding the localization of element concentrations in the edge areas of a horizontally manufactured continuous casting made of alloyed non-ferrous metals.
In the horizontal continuous casting of non-ferrous metal alloys, such as tin-bronze strips, and particularly those castings having a rectangular cross-section, there continue to be problems with respect to obtaining reliable information about the quality of the continuous castings, in spite of intense efforts in the field to overcome this deficiency. These difficulties mainly become evident when tin concentrations (tin segregations) are detected which exceed the alloy specification by some multiple. Such tin concentrations are anomalies which occur in the edge areas of the continuous casting over the entire length of the strip, extending mainly in the direction of casting, and as a rule are always present in a tin-bronze alloy. In practice, they are normally eliminated by removing a surface layer having a specific thickness, so that downstream, products of satisfactory quality can then be produced from such a continuous casting.
The thickness of the removed surface layer has heretofore been determined on the basis of values from experience which were sufficient for the normal case. However, under certain conditions during horizontal casting, tin concentrations are formed which extend beyond what is typical into the continuous casting at specific locations. The causes for this are usually intended or unintended changes in the cooling conditions. However, these anomalies only become evident in the form of bright yellow linear stripes on rolled and polished surfaces after several work operations have already been carried out. These lots are then generally scrapped.
The object of the present invention is to provide a method and apparatus for the localization of element concentrations in the edge areas of a horizontally manufactured continuous casting of alloyed non-ferrous metals, in which element concentrations can be reliably detected and eliminated in the event of changes to the cooling conditions present, whether intended or not, as well as regardless of an optionally implemented local homogenization cooling.
Accordingly, within the framework of the invention, a longitudinal section is removed as a test specimen from the continuous casting at the start and end of a coil to be wound, and a surface layer is removed from this test specimen in the transverse direction. The surface layer has a defined thickness and is in the form of a strip. The surface layer can be removed by milling, grinding or another type of mechanical machining. It is important that no lubricating agents be added during removal. The removal takes place over the total length of the test specimen, and thus of the width of the continuous casting.
Subsequently, a point-by-point spectroanalysis of the metal composition is carried out in linear sequence on these exposed strips of the test specimen in its longitudinal direction. The element concentrations determined in this connectionxe2x80x94the tin concentrations in the case of a tin-bronze stripxe2x80x94are then displayed numerically and graphically with the aid of a computer.
If in so doing, it is determined that an element concentration in excess of the specified upper limit exists at at least one location, an additional layer is then removed along the strip, the additional layer being distinctly thinner than the first layer. Thereupon, the spectroanalysis of the material composition is again carried out in the longitudinal direction of the strip and the result is displayed. If the element concentration now remains below the limiting value, the continuous casting is released for the production of finished products or for further processing. If unacceptable anomalies are still present, a thin layer is again removed, a further spectroanalysis is then carried out, and after that a decision is made as to whether the continuous casting can be sent on for further processing.
Therefore, the method according to the invention permits precise determination of how much material must be removed from the continuous casting, so that an acceptable starting material can be made available for further processing.
This device has a sensor determining the position of the test specimen, a metal-removal unit and a spectral-analysis head which are displaceable relative to the test specimen and are placed under the influence of a metal-removal and analysis control unit that is coupled to a computer via a programmable controller and via a spectrometer, respectively. The computer has a monitor and a printer.
The test specimen removed from the continuous casting is fixed in place. The sensor then scans the surface of the test specimen and adjusts the metal-removal unit, in particular a milling head with milling cutter, in such a way that it can be used to remove a surface layer of uniform thickness. At the same time, the extension in the transverse direction is determined. The sensor is under the influence of a metal-removal and analysis control unit which is coupled to a programmable controller. The controller is in turn connected to a computer which positions the sensor stepwise via the controller and the metal-removal and analysis control unit, and in addition monitors all safety chains and functions of the device.
A predetermined layer thickness, 0.6 mm for example, is subsequently removed by the metal-removal unit in the WE form of a strip, resulting in a clean surface. The spectral-analysis head is run over this strip determining the metal composition point by point in linear sequence, the spectrometer also transmitting the concentration to the computer.
Since the computer collects all positioning and analysis data and also corrects the analysis data with reference to the calibration values, the analysis and positioning data are transferred into a diagram which is then displayed online on the computer""s monitor. Here, it can be clearly discerned where an anomaly that may exceed the limiting values is present. If the computer detects such an anomaly, it immediately orders the metal-removal unit to remove an additional layer from the longitudinal section, this time, however, of a lesser thickness such as 0.2 mm. This may be carried out over the entire extension in the transverse direction of the longitudinal section, or only where the excess concentration was previously determined.
After removal of the second layer, a spectroanalysis is undertaken once more and it is determined whether the elevated concentration is still present or whether the element concentrations are within the limiting values. If they are within the limiting values, the anomaly is defined as acceptable, so that the values are then also defined for the machining of the continuous casting. If the anomaly is still present, an additional thin layer of 0.2 mm, for example, is removed and the test specimen is subsequently subjected to spectroanalysis.
In a further development of the idea according to the invention, it is advantageous for the metal-removal and analysis control unit to be connected to the spectrometer via an optical waveguide.